Tubular system operators are always receptive to new methods and devices to permit actuation of tubular tools such as those in industries concerned with earth formation boreholes, such as hydrocarbon recovery and gas sequestration, for example. It is not uncommon for various operations in these industries to utilize a temporary or permanent plugging device against which to build pressure to cause an actuation.
Sometimes actuating is desirable at a first location, and subsequently at a second location. Moreover, additional actuating locations may also be desired and the actuation can be sequential for the locations or otherwise. Systems employing droppable members, such as balls, for example, are typically used for just such purpose. The ball is dropped to a ball seat positioned at the desired location within the borehole thereby creating the desired plug to facilitate the actuation.
In applications where the first location is further from surface than the second location, it is common to employ seats with sequentially smaller diameters at locations further from the surface. Dropping balls having sequentially larger diameters allows the ball seat furthest from surface to be plugged first (by a ball whose diameter is complementary to that seat), followed by the ball seat second furthest from surface (by a ball whose diameter is complementary to that seat) and so on.
The foregoing system, however, creates increasingly restrictive dimensions within the borehole that can negatively impact flow therethrough as well as limit the size of tools that can be run into the borehole. Additionally, the number of discrete ball/seat combinations that can be run is limited as a result of the increasingly restrictive dimensions. Systems and methods that allow operators to increase the number of actuatable locations within a borehole without the drawbacks mentioned would be well received in the art.